Quick answer. Use RCS instead of SMS when your audience is RCS-capable and the message benefits from branding, rich media, interactivity, or measurement — which covers most marketing and many transactional flows. Promotions with images, order and delivery updates with tracking, appointment reminders with confirm/reschedule buttons, loyalty and rewards, and two-way support all perform better as RCS. The branded, verified format also matters most exactly where trust matters — offers, account alerts, and fraud notifications.
A simple rule: lead with RCS for anything where a logo, an image, a button, or a read receipt makes the message work harder, and let SMS handle the fallback automatically. You don't have to choose per audience — the system sends RCS where it can and SMS where it can't.